Dielectric films on substrates have many uses. For example, a thin film field effect transistor (“TFET”) or other active microelectronic device can be fabricated that incorporates a dielectric film on a conductive substrate. Further, a capacitor can be fabricated that incorporates a dielectric film to isolate two conductive electrodes. In these types of devices and others, the effective dielectric constant and the capacitance of the dielectric film play important roles in determining the overall device performance.
As the thickness of a dielectric film is increased, its capability to act as an insulator also increases. The incidence of pinholes passing completely across the thickness of the dielectric film from one surface to the other (“through holes”) also accordingly decreases. However, as the thickness of the dielectric film is increased, the dielectric film's capacitance may decrease. In an exemplary TFET, as the thickness of the dielectric film is increased, the ability of the gate electrode to affect the conductivity of the channel region of the semiconductor is weakened. In an exemplary capacitor, the capacitance of the device decreases as the separation between the two conductive substrate plates increases. Hence, the performance capability of the capacitor in storing an electrical charge decreases.
The desirability of avoiding through holes in dielectric films resulting in charge leakage and shorting, and the desirability of high capacitance, accordingly call for conflicting designs with relatively increased and decreased dielectric film thickness, respectively.
There is a need for dielectric films having a reduced thickness and an accordingly high capacitance, also having a reduced prevalence of through holes.